According to treatment of a decayed and/or infected tooth done in a dental clinic setting, the decayed portion of the tooth is first removed with a dental handpiece. When the pulp of the tooth is injured, the injured or affected pulp is removed. A root canal is sealed by filling the root canal chamber of the injured pulp with a filler (endodontic cement or sealer), and a prosthetic treatment is then performed on the tooth. In the root canal filling procedure, gutta-percha cones are used as a temporary filling material having an auxiliary function for enabling the filler to penetrate into the root canal and thus to seal up the root canal. Gutta-percha, which is a natural vegetable extract, has a semi-solid phase at room temperature, but has the form of a solid gum when it is compressed or heated. This is called “white gutta-percha.”
In endodontic treatment of a decayed tooth, the affected pulp of the tooth is first prepared to remove affected nerve tissues. Thereafter, filler is coated on a root canal wall in order to prevent the root canal from being further affected by another source of infected area. A gutta-percha cone having a suitable size is then inserted into the root canal to fix the filler to the main and accessory portions of the root canal.
With a conventional endodontic instrument, a needle is not bent. Thus, the operator bends the needle in a desired treatment direction when he/she performs a dental treatment, and the operator bends the needle in an opposite direction when he/she performs a dental treatment in an opposite direction. If the needle is bent during use, a thin film of the needle may be cracked or separated. If the operator loosens the needle, turns it in an opposite direction and then re-fixes it in order to avoid the re-bending of the needle after performing the dental treatment in one direction, the already heated needle is difficult to manipulate. The gutta-percha may leak out during the procedure of loosing and re-fixing the needle. The manipulation of the needle is troublesome.
To solve such a problem, Korean Patent Application No. 10-2005-0044248, entitled “Complete melting type wireless charger for endodontic treatment, was filed by the present inventor.
More specifically, as illustrated in FIG. 1, the endodontic instrument, filed by the present inventor, includes a main body 10, a heater 20, a charge switch 30, an injection member 40, a grasp unit 50, and a needle unit 100. A power supply is built in the main body 10, and the injection member 40 is operated by the manipulation of the charge switch 30. The injection member moves the mounted gutta-percha to the needle unit 100.
In addition, as illustrated in FIG. 2, the needle unit 100 includes a needle 110, a needle unit body 120, and a sealing member 140. The needle 110 discharges the molten gutta-percha to a desired location. The needle 110 is bent at a predetermined angle in order for an operator's more convenient working and includes a silver alloy pipe combined with copper alloy or SUS.
A proximal end where the needle 110 is connected to the needle unit body 120 is about 0.9 mm in diameter. A distal end is tapered for suitable dental treatment and is about 0.5 mm to 0.9 mm in diameter. In order to rotatably connect the needle 100 to the needle unit body 120, a rectangular coupling portion 111 having a larger diameter than the needle is formed at the proximal end of the needle connected to the needle unit body.
The needle unit body 120 includes a screw coupling unit on an outer periphery such that it can be connected to the main body. A rectangular coupling groove corresponding to the rectangular coupling portion 111 of the needle is formed inside the needle unit body 120. When the rectangular coupling portion of the needle is inserted into and connected to the rectangular coupling groove of the needle unit body, the needle is 360-degree rotatable, so that the operator can use the needle while rotating it at a desired angle.
However, it is difficult to perform a process of forming the rectangular coupling groove inside the needle unit body. The needle may not be well rotated due to the attachment force generated according to the coupling degree between the rectangular coupling portion and the rectangular coupling groove. If the coupling degree between the rectangular coupling portion and the rectangular coupling groove is too loose, the needle may be easily rotated in an unintended direction. Furthermore, the needle may be released from the needle unit boy 120.